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Full text of "Handbook Of Chemical Engineering - I"

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82
CHEMICAL ENGINEERING
Where,
F = Fuel charge per hour (see Table 3 and price of coal), L = Labor charge per hour (see Table 4 and labor rates), E - Incidental expenses 0.7 to 1.0 ct. per ton rating per hour, T = Task duration (yearly) in hours, B = Burden 0.165 X ($400 to $500), and Q = Capacity in tons per hour (see Formula (2)). Example 1.—Required economic size and net operating cost (C) of locomotive
crane for handling 50,000 gross tons (56,000 net tons) of loose material weighing
60 Ib. per cubic foot within a period of 100 8-hr, days per year.
		Task Duration	
Size of crane, tons	Q, formula (2), tons		
			
		Hours	Days
10	42	1,334	Over 100
15	63	889	Over 100
20	84	667	83+     .
25	105	534	66 +
30	126	444	55 +
Assume.—-Cost of fuel, $6 per ton (2,000 Ib.) = $0.003 per pound,
Labor—engineer.................................. $1.00 per hour
Labor—helper.................................... $0.60 per hour
Incidental expenses, average—0.85 ct. per ton rating per hour; Initial  cost, $450 per ton rated capacity. Twenty-ton locomotive crane—Formula (3):
r - (160 X 0.003  +   (1   +  1,2)   +  20   X   0.00085)667 + 0.165 X 450 X 20 °                                                         56,000             "                                    ~
= $0.0586—Net operating cost per ton. Twenty-five-ton locomotive crane:
r = (200  X  0.003  +   (1  +  1.2)   +  25   X 0.00085)534 + 0.165 X 450 X 25
56,000
= $0.0600—Net operating cost per ton. Thirty-ton locomotive crane:
C = (240  X  0.003  +   (1   +  1.2)   + 30 X 0.00085)444 +JU65_X __460_X^30
56,000 = $0.0631—Net operating cost per ton.
Result.—Economic size, 20-ton locomotive crane, net operating cost, 5.86 cts. per ton.
Example 2.—Required net cost of handling 80,000 net tons of loose material weighing 102 Ib. per cubic foot with a 25-ton locomotive crane and the duration of the task.
Q = 0.07 X 25 X 120 = 210 tons per hour—formula (2). Task  duration: 80,000 -r-210 = 381   hr.,   47%   8-hr.   days.
Assume.—Cost of fuel, $6 per ton = $0.003 per pound.
Labor f enSineer..................................  $1.00 per hour
1 helper.................................... $0.60 per hour
Incidental expenses, average—0.90 ct. per ton rating per hour. Initial cost of crane, $400 per ton rated capacity.